A solid-phase support is used for the purpose of detecting and separating a target substance such as a protein, a nucleic acid and a cell from sample such as blood. As the method of detection and separation using a solid-phase support, a general method is that a ligand is fixed to a solid-phase support, with which a sample is brought into contact to allow a target substance to react with the ligand. At the time of the above contact, however, the target substance and impurities in the sample nonspecifically adsorb on a surface of the solid-phase support instead of the ligand, which may cause noise.
Therefore, for the purpose of suppressing the above nonspecific adsorption, a technique is suggested, in which an atom transfer radical polymerization initiating group (ATRP initiating group) is introduced on the surface of the gold film chip in a magnetic biosensor in a content amount and a specific carboxybetaine monomer is polymerized from such ATRP initiating group to form a polymer brush (JP 2009-69141 A).
A ligand is, however, hard to bind to the above gold film chip having a polymer brush, which may not sufficiently grasp a target substance.
In the meantime, an interest has focused on a magnetic bead as a solid-phase support used for a diagnostic agent for enzyme immunoassay in a clinical examination in recent years. Early detection of diseases, for example, is required, and thus it is demanded that the magnetic bead used for the diagnostic agent is sufficiently grasp a target substance.